Vehicle air conditioning (A/C) systems are closed heat exchange systems designed to function with a specific refrigerant as the primary heat exchange medium. Refrigerants used in these systems include, dichlorodifluoromethane, commonly referred to as R-12, tetrafluoroethane, commonly referred to as R-134a, 2,3,3,3-tetrafluoropropene, or R-1234yf, and difluoroethane, or R-152a.
Refrigerant recovery units are used for the maintenance and servicing of vehicle A/C systems, which may include, for example, the recovery, evacuation, recycling and/or recharging of the refrigerant in the A/C systems. A refrigerant recovery unit may be a portable system that connects to the A/C system of a vehicle to recover refrigerant out of the system, separate out contaminants and oil, and/or recharge the A/C system with additional refrigerant.
When refrigerant from an A/C system is recovered by a refrigerant recovery unit, there is sometimes an amount of air recovered into the unit. As part of the recycling process, any recovered air is collected in the refrigerant storage tank of the refrigerant recovery unit and purged prior to the refrigerant being charged back into the A/C system. There is always some refrigerant that is lost along with the air being purged during the purge process. Typically, the amount of refrigerant lost is small because the amount of air that needs to be purged is small. However, as the amount of air that needs to be purged increases, the amount of refrigerant lost during the purge process increases. Due to the high cost of some of the newer refrigerants, such as R-1234yf, reducing the amount of refrigerant loss can have economic benefits to those providing A/C system services, as well as to the consumers of those services. In addition to the financial impact, there are also safety and environmental reasons to minimize refrigerant loss. For example, again in the case of R-1234yf, the refrigerant is flammable, so reducing the amount of refrigerant loss during the air purge process will reduce the likelihood of creating a hazardous situation. As for the environmental impact, all refrigerants have some environmental impact and there always exists a goal of minimizing or eliminating that impact.
A need exists for methods and systems that will minimize refrigerant loss during a purge process of the refrigerant recovery units.